2D SIDE SCROLLING WITH XNA - LECTURE 15: 2D SPRITE GRAPHICS

Công Nghệ Thông Tin, it, phầm mềm, website, web, mobile app, trí tuệ nhân tạo, blockchain, AI, machine learning - Báo cáo khoa học, luận văn tiến sĩ, luận văn thạc sĩ, nghiên cứu - Công nghệ thông tin gamedesigninitiative at cornell university the 2D Sprite Graphics Lecture 15 gamedesigninitiative at cornell university the Graphics Lectures — Drawing Images — SpriteBatch interface — Coordinates and Transforms — Drawing Perspective — Camera — Projections — Drawing Primitives — Color and Textures — Polygons 2D Sprite Graphics bare minimum to draw graphics side-scroller vs. top down necessary for lighting shadows 2 gamedesigninitiative at cornell university the Take Away for Today — Coordinate Spaces and drawing — What is screen space? Object space? — How do we use the two to draw objects? — Do we need any other spaces as well? — Drawing Transforms — What is a drawing transform? — Describe the classic types of transforms. — List how to use transforms in a game. 2D Sprite Graphics3 gamedesigninitiative at cornell university the The SpriteBatch Interface — In this class we restrict you to 2D graphics — 3D graphics are much more complicated — Covered in much more detail in other classes — Art 1701: Artist tools for 3D Models — CS 4620: Programming with 3D models — In XNA, use the interface SpriteBatch — Sprite: Pre-rendered 2D (or even 3D) image — All you do is composite the sprites together 2D Sprite Graphics4 gamedesigninitiative at cornell university the — Use coordinate systems — Each pixel has a coordinate — Draw something at a pixel by — Specifying what to draw — Specifying where to draw — Do we draw each pixel? — Use a drawing API — Given an image; does work — This is what XNA provides 2D Sprite Graphics Drawing in 2 Dimensions y x (2,4) (-1,-1) 5 gamedesigninitiative at cornell university the Sprite Coordinate Systems — Screen coordinates: where to paint the image — Think screen pixels as a coordinate system — Very important for object transformations — Example: scale, rotate, translate — In 2D, origin is typically top left of screen — Object coordinate: location of pixels in object — Think of sprite as an image file (it often is) — Coordinates are location of pixels in this file — Unchanged when object moves about screen 2D Sprite Graphics6 gamedesigninitiative at cornell university the Sprite Coordinate Systems +y (0,0) +x Object: (0,0) Screen: (300,200) 2D Sprite Graphics7 gamedesigninitiative at cornell university the Drawing Sprites — Basic instructions: — Set origin for the image in object coordinates — Give the SpriteBatch a point to draw at — Screen places origin of image at that point — What about the other pixels? — Depends on transformations (rotated? scaled?) — But these (almost) never affect the origin — Sometimes we can reset the object origin 2D Sprite Graphics8 gamedesigninitiative at cornell university the Sprite Coordinate Systems +y (0,0) +x Object: (0,0) Screen: (300,200) 2D Sprite Graphics9 gamedesigninitiative at cornell university the Sprite Coordinate Systems 2D Sprite Graphics10 gamedesigninitiative at cornell university the Sprite Coordinate Systems +y (0,0) +x Object: (0,50) Screen: (300,200) 2D Sprite Graphics11 gamedesigninitiative at cornell university the Drawing with SpriteBatch Draw(GameTime time) { … spriteBatch.Begin(); spriteBatch.Draw(image0,origin0,color0); spriteBatch.Draw(image1,origin1,color1); … spriteBatch.End(); … } 2D Sprite Graphics screen coordinates 12 gamedesigninitiative at cornell university the 2D Transforms — A function T : R2→R2 — “Moves” one set of points to another set of points — Transforms one “coordinate system” to another — The new coordinate system is the distortion — Idea: Draw on paper and then “distort” it — Examples: Stretching, rotating, reflecting — Determines placement of “other” pixels — Also allows us to get multiple images for free 2D Sprite Graphics13 gamedesigninitiative at cornell university the The “Drawing Transform” — T : object coords → screen coords — Assume pixel (a,b) in art file is blue — Then screen pixel T(a,b) is blue — We call T the object map — By default, object space = screen space — Color of image at (a,b) = color of screen at (a,b) — By drawing an image, you are transforming it — S an image; transformed image is T(S) 2D Sprite Graphics14 gamedesigninitiative at cornell university the Example: Translation — Simplest transformation: T(v) = v + u — Shifts object in direction u — Distance shifted is magnitude of u — Used to place objects on screen — By default, object origin is screen origin — T(v) = v + u places object origin at u 2D Sprite Graphics S T(S) 15 gamedesigninitiative at cornell university the Composing Transformations — Example: T : R2→R2, S : R2→R2 — Assume pixel (a,b) in art file is blue — Transform T makes pixel T(a,b) blue — Transform ST makes pixel S(T(a,b)) blue — Strategy: use transforms as building blocks — Think about what you want to do visually — Break it into a sequence of transforms — Compose the transforms together 2D Sprite Graphics16 gamedesigninitiative at cornell university the Application: Scrolling 2D Sprite Graphics Screen World World origin Screen origin 17 gamedesigninitiative at cornell university the Application: Scrolling 2D Sprite Graphics Screen World World origin Screen origin Object origin 18 gamedesigninitiative at cornell university the Scrolling: Two Translations — Place object in the World at point p = (x,y) — Basic drawing transform is T(v) = v+p — Suppose Screen origin is at q = (x’,y’) — Then object is on the Screen at point p-q — S(v) = v-q transforms World coords to Screen — ST(v) transforms the Object to the Screen — This separation makes scrolling easy — To move the object, change T but leave S same — To scroll the screen, change S but leave T same 2D Sprite Graphics19 gamedesigninitiative at cornell university the Scrolling: Practical Concerns — Many objects will exists outside screen — Can draw if want; graphics ca...

the gamedesigninitiative at cornell university Lecture 15 2D Sprite Graphics Graphics Lectures —  Drawing Images bare minimum to draw graphics —  SpriteBatch interface —  Coordinates and Transforms side-scroller vs top down —  Drawing Perspective necessary for —  Camera lighting & shadows —  Projections the —  Drawing Primitives gamedesigninitiative —  Color and Textures —  Polygons at cornell university 2 2D Sprite Graphics Take Away for Today — Coordinate Spaces and drawing —  What is screen space? Object space? —  How do we use the two to draw objects? —  Do we need any other spaces as well? — Drawing Transforms —  What is a drawing transform? —  Describe the classic types of transforms —  List how to use transforms in a game the 3 2D Sprite Graphics gamedesigninitiative at cornell university The SpriteBatch Interface — In this class we restrict you to 2D graphics —  3D graphics are much more complicated —  Covered in much more detail in other classes — Art 1701: Artist tools for 3D Models — CS 4620: Programming with 3D models — In XNA, use the interface SpriteBatch —  Sprite: Pre-rendered 2D (or even 3D) image —  All you do is composite the sprites together the 4 2D Sprite Graphics gamedesigninitiative at cornell university Drawing in 2 Dimensions —  Use coordinate systems y (2,4) —  Each pixel has a coordinate —  Draw something at a pixel by x (-1,-1) —  Specifying what to draw —  Specifying where to draw —  Do we draw each pixel? —  Use a drawing API —  Given an image; does work —  This is what XNA provides the 5 2D Sprite Graphics gamedesigninitiative at cornell university Sprite Coordinate Systems —  Screen coordinates: where to paint the image —  Think screen pixels as a coordinate system —  Very important for object transformations —  Example: scale, rotate, translate —  In 2D, origin is typically top left of screen —  Object coordinate: location of pixels in object —  Think of sprite as an image file (it often is) —  Coordinates are location of pixels in this file —  Unchanged when object moves about screen the 6 2D Sprite Graphics gamedesigninitiative at cornell university Sprite Coordinate Systems (0,0) +x Object: (0,0) Screen: (300,200) +y 2D Sprite Graphics the 7 gamedesigninitiative at cornell university Drawing Sprites — Basic instructions: —  Set origin for the image in object coordinates —  Give the SpriteBatch a point to draw at —  Screen places origin of image at that point — What about the other pixels? —  Depends on transformations (rotated? scaled?) —  But these (almost) never affect the origin — Sometimes we can reset the object origin the 8 2D Sprite Graphics gamedesigninitiative at cornell university Sprite Coordinate Systems (0,0) +x Object: (0,0) Screen: (300,200) +y 2D Sprite Graphics the 9 gamedesigninitiative at cornell university Sprite Coordinate Systems the 10 2D Sprite Graphics gamedesigninitiative at cornell university